How to tell if you're in a login shell?

In bash if you run echo $0 you’ll get -bash for login shells and bash for non-login shells. The bash manual says this:

A login shell is one whose first character of argument zero is a -, or one started with the --login option.

Other shells work similarly. However if I try to do the equivalent echo @args[0] in Ion, I get:

ion: expansion error: invalid index

What would be the proper way to detect if I’m in a login or non-login shell in Ion?

The problem I’m trying to solve is that I want a command to run every time I login, but not every time I open a terminal.

I found the answer in the manual. There’s a status builtin that does just that: